Conferencing allows multiple users to participate in the same call on a dynamic basis. A single call can be established and additional users can be added or deleted on a dynamic basis.
FIG. 1 illustrates a representative prior art digital telephony conferencing system. The conferencing system consists of numerous participants at locations 1 through n. One or more telephones 5 may be located at each location. A multiplexing and demultiplexing device 4 connects each of the telephones to the conference bus 3. Some locations may have only a single user, while other locations may have multiple users. Each user will be individually connected through a multiplexer 4. A time-division multiplexing (TDM) bus 3 conveys the signal information generated by each participant to all other participants of the system.
FIG. 2 illustrates the use of a single core for processing the signals from the various locations illustrated in FIG. 1. All of the telephones 5 are connected to a common core, such as a DSP core 7. The DSP core 7 has a number of channels, each participant telephone 5 is accommodated by a channel. Each channel acts as a router for receiving the audio signals from the telephone connected to the channel. The core 7 also has a plurality of mixers 8 for providing audio signals out to each of the telephones 5. The mixer for each telephone sums the signals for all other telephones and provides this signal to the particular telephone served by that mixer. The mixer does not provide a telephone with its own signal because the speaker would hear an echo of his own voice.
Each of the signals from each of the telephones has noise associated with the signal. The noise can be background noise or other noise. The mixing operation, a summation of all signals, causes the noise level to increase at each of the telephones. The increase in noise can limit the number of participants and/or can have an adverse impact on the quality of the communication.
The use of a single core for a conference call also reduces the total number of participants which is limited by the number of channels on a single core. Further, the transmission of background noise, as well as the transmission of other speakers in addition to the primary speaker places an additional load on a communications system.
When a large number of people participate in a telephony conference, there is a significant likelihood that two or more participants will speak at the same time. It is also likely that background noise originating at one or more group nodes will be transmitted through the conferencing system. The transmitted signals of the background noise and multiple speakers interfere with the signal that is of interest to the conference participants. These interfering signals impair the ability of the conference listeners to hear and understand the speaker that is of interest to them and thereby reduce the quality of the communication.